JP2521042B2 - Speed control system - Google Patents

Description

The present invention relates to a rotation speed control system for driving an electric motor with a variable frequency power supply.

[Conventional technology]

FIG. 4 is a connection diagram of a conventional rotation speed control system,
In the figure, 1 is a commercial power source, 2 is a variable frequency power source (hereinafter
VVVF) 4 is a switch, 5 is an electric motor, 6 is a rotating body such as a fan, 8 is a damper drive device, 8a and 8b are drive bodies and dampers (main body) of the damper drive device 8, and 10 and 11 are Inlet and outlet of fluid such as air, which is a load, P is a setting signal from a setting device (not shown) that sets the required air volume, and Q is a measurement signal of a measuring device (not shown) that measures the load air amount. , SG
Signal generator that regulates the opening of damper 8b during VVVF operation, H
Is a deviation detector for detecting the deviation between the setting signal P and the setting signal Q, S is a proportional integrator, AD is an adder, E / I is a voltage / current converter, and E / P is a voltage / pressure converter.

The following operation will be described. Setting signal P and measurement signal Q
First, the case where the values match with each other, that is, the time when there is no load change will be described. At this time, since the output of the deviation detector H is 0, the output of the integrator S is a constant value, and accordingly, the value (voltage) is converted into a current to keep the output frequency of VVVF2 at a predetermined value. The rotation speeds of the electric motor 5 and the fan 6 are maintained at predetermined values.

On the other hand, since the output of the deviation detector H is 0, the output of the adder AD becomes the same value as the output of the signal generator SG of the specified value, and this value is converted into pressure by the voltage / pressure converter E / P and the damper The damper 8b, which is given to the drive device 8 and holds the damper 8b at a specified opening via the drive rod 8a, results in that the amount of air passing from the inlet 10 to the outlet 11 has a value corresponding to the measurement signal Q. Become.

Next, the case of increasing or decreasing the load will be described. In order to make the explanation in this case easy to understand, the state of change is shown in FIG.

At time t ₁ , when the setting signal P becomes large, the measurement signal Q is still the value before the change, and therefore the output of the deviation detector H increases by the change amount of the setting signal P and the integral The output of the device S is gradually increased to increase the rotation speed of the electric motor 5,
Since the air flow rate is increased, the measurement signal Q is gradually increased.

On the other hand, the output of the deviation detector H is added to the output of the specified signal generator SG by the adder AD to form a combined output (see FIG. 2A).
D), converted into pressure and given to the damper drive device 8,
The opening θ of the damper 8b is made large (in the direction of increasing the air amount).

Due to the synergistic effect of increasing the speed of the electric motor 5 and the opening θ of the damper 8b, the air flow rate Q responsively rises to a desired value, the deviation between the setting signal P and the measurement signal Q gradually decreases, and finally reaches 0. Then (time t ₂ ), the output of the integrator S is stabilized to a new value, the rotation speed of the electric motor 5 is stabilized, and the damper 8b
Therefore, the opening degree of is returned to the specified value θc.

Then, At a time t _3, it will be described the setting signal P has come small. As in the case of the increase, the output of the deviation detector H is reduced by the decrease change of the setting signal P, and as a result, a decrease in the rotation speed of the electric motor 5 and a decrease in the opening θ of the damper 8b are induced. Due to the synergistic effect, the air flow rate Q rapidly decreases to a predetermined value.

FIG. 6 is a characteristic example showing the relationship between the damper opening and the output air volume (the air volume when the damper opening is 90 ° is 100%).
From the figure, it is shown that the output air volume changes little with changes in the damper opening when the damper opening is 70 ° to 90 °.

Therefore, in the system configuration of FIG. 4, in order to effectively control the increase / decrease of the air flow, the damper opening degree is usually set to about 50 ° (at least 60 ° or less).

[Problems to be solved by the invention]

Since the conventional rotation speed control system is configured as described above, it is intended to move the damper in the opening direction to increase the load and to speed up the control response.
In order to improve controllability, the damper opening must be set to around 50 °, and there was a problem that the energy saving effect was smaller than when operating near full opening of the damper.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a rotation speed control system capable of sufficiently ensuring a response speed with respect to a load increase / decrease without sacrificing the energy saving effect. .

[Means for solving problems]

The rotation speed control system according to the present invention operates the damper in the closing direction only when the load decreases, and responds to the increase in the load only by increasing the rotation speed. Near (generally, damper opening is about 70 ° or more)
And so on.

[Work]

The rotation speed control system according to the present invention prevents the energy saving effect from decreasing by operating the damper opening in the vicinity of full opening.

〔Example〕

An embodiment of the present invention will be described below. In FIG. 1, GATE is a gate circuit, and the other components are the same as those in FIG.

Next, the operation will be described. The gate circuit GATE has an input / output characteristic as shown in FIG. 2,
The output of the deviation detector H is used as an input, and when the input is positive (positive), the output is 0, and when the input is negative (negative), the input is directly output.

Next, the operation of FIG. 1 will be described with reference to FIG. 3 showing the signal waveform of each part. First, when the set signal P and the measured signal Q match, the electric motor is at a constant rotation speed, and the damper 8b is at a specified opening degree, as in the conventional FIG.

Consider the case where the setting signal P becomes large at time t ₁ and the output H = P−Q of the deviation detector increases (positive). The output of the gate circuit GETE is 0, and the damper opening is the specified opening θ.
c is fixed. On the other hand, the output of the deviation detector H is given to the integrator S to increase its output, increase the output frequency of VVVF2, increase the rotation speed of the motor (electric motor) 5, and consequently increase the air volume as a load. Increase the value to the value of the setting signal P.

The response to this large air volume is performed by VVVF2,
If the acceleration torque of the motor 5 is increased, the speed can be increased to the extent that there is no practical problem. To increase the acceleration torque of the motor 5, it is necessary to increase the power supply capacity of VVVF2.
Has a little extra capacity in normal capacity and can handle it sufficiently.

Then, at time t _3, describes the time setting signal P has come small. In this case, the output of the deviation detector H is decreased (negative), and the gate circuit GATE outputs the output. Therefore, as in the case described with reference to FIG. 4, the rotation speed is decreased and the damper opening is operated in the closing direction. .

Since it operates as described above, the damper opening needs to have controllability only in the closing direction from the specified opening. Therefore, the specified opening is selected to a value near full opening (for example, 70 ° to 80 °). Therefore, the energy saving effect is significant.

In the above embodiment, the fan 6 is used as the load of the electric motor 5.
However, other rotating bodies such as a pump and a compressor may be used, and accordingly, the damper 8b may be another mechanical control means.

Further, although air is described as the load in the above embodiment, any other fluid such as water has the same effect as that of the above embodiment.

Further, the outputs of the integrator S and the adder AD are given to the VVVF2 and the damper driving device 8 through the voltage / current converter E / I and the voltage / pressure converter E / P, respectively, as long as they are suitable for control. It is obvious that other first means and second means may be used. Although the signal generator SG is described as outputting a specified value, it may be a function such as the number of revolutions or the air volume.

In the above embodiment, in order to slightly delay the response sensitivity to the setting signal P of the setter (not shown) changing many times in a short time, the output change of the adder AD is delayed to some extent. May be given to ensure the stability of control.

Further, in the above embodiment, the negative value of the output of the deviation detector H is directly used as the output of the gate circuit GATE, but the output corresponding to the negative value such as a proportional value is used as the output of the gate circuit GATE. You may

〔The invention's effect〕

As described above, according to the present invention, when the deviation detected by the deviation detector indicates an increase in the rotation speed of the electric motor, the deviation detector blocks the output to the adder, and the deviation Is designed to decrease the rotation speed of the electric motor, the output of the deviation detector is applied to the adder as it is. The specified opening can be set to near full opening, so that there is an effect that a rotation speed control system having an excellent energy saving effect can be obtained.

[Brief description of drawings]

FIG. 1 is a connection diagram showing a rotation speed control system according to an embodiment of the present invention, FIG. 2 is an input / output characteristic diagram, FIG. 3 is a signal waveform diagram of each part of FIG. 1, and FIG. Fig. 5 is a connection diagram showing the number control system, Fig. 5 is a signal waveform diagram of each part in Fig. 4,
FIG. 6 is a diagram showing damper characteristics. 2 is a variable frequency power supply (VVVF), 5 is an electric motor, 6 is a rotating body, 8 is control means, P is a setter signal, Q is a measuring instrument signal,
SG is a signal generator, H is a deviation detector, S is an integrator, AD is an adder, E / I is a voltage / current converter (first means), and E / P is a voltage / pressure converter (second). Means), GATE is a gate circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A deviation detector for detecting a deviation between a set value of a setter for setting the amount of fluid which is a load of a rotating body and a measured value of a measuring instrument for measuring the amount of fluid, and the deviation detector. The integrator that proportionally integrates the deviation detected by, the variable frequency power source that controls the electric motor that drives the rotating body based on the proportional integration result of the integrator, and the opening degree of the damper that controls the amount of the fluid. When the signal generator to be set and the deviation detected by the deviation detector indicate an increase in the rotation speed of the electric motor, zero is output, and the deviation indicates a decrease in the rotation speed of the electric motor. If it is, a gate circuit that outputs the output of the deviation detector as it is, an adder that adds the output of the gate circuit and the set value of the signal generator, and an addition result of the adder. Drive the damper Rotational speed control system including a path drive.